Spray nozzle distributors are widely used in distillation and absorption units to provide a uniform liquid distribution to the upper surface of packed beds. For example, in typical crude oil vacuum distillation units, wash oil is sprayed from the spray nozzles onto a wash bed to remove contaminants from a feed vapor or flash zone vapor. Spray nozzle distributors are more resistant to plugging and coking than other types of distributors. However, the use of spray nozzles can lead to a significant entrainment of the wash oil.
The wash oil entrainment must be estimated to determine the net wash oil flow rate that reaches the wash bed. Although the amount of entrainment depends on the actual operating conditions, the total wash oil flow rate is generally kept constant at its design value during operation of distillation units, without accounting for variations in process conditions that occur during operation. Such practice fails to optimize the net wash oil flow rate as the operating conditions in distillation units may vary, especially with changes to the feed rate.
Alternatively, it is known in the art to adjust the total wash oil flow rate proportionally to the feed rate (i.e., maintain a constant ratio of the total wash oil rate to the feed rate). See, e.g., EPO pat. publ. no. 2072602A1 to Chiyoda Corp. (publ. June 2009). However, this practice may not provide an optimum net wash oil rate, and could lead to coke formation of the wash bed and unscheduled shutdowns. This and all other extrinsic materials discussed herein are incorporated by reference in their entirety. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
Thus, there is still a need for systems and methods that allow for continuous optimization of a net wash oil flow rate in distillation units.